A new sample testing technology is developed that would allow manufacturing to test RFID tag samples for mass production in a non-destructive process that is as effective as conventional testing that uses a destructive process.
TransCore produces millions of RFID tags every year for highway toll collections, where the RFID tags are attached on the windshield inside vehicles. The accuracy of testing tags requires careful considerations, since RFID performance is very sensitive to the care of installation and glass thickness. In other words, accurate installation and glass thickness should be considered as part of the antenna.
RFID tags are made of a number of thin plastic layers on which are printed antennas and to which are attached an ASIC and adhesive backing for the customer to install the tags in the windshield permanently. The RFID tags weigh 2 grams and measure approximately 3.119″ (L)×2.647″ (W)×0.014″ (Thick, approximately 0.050″ at ASIC). The tag consists of a laminate of multiple layers of polymer films, inks, and adhesive materials. The ASIC in a thin small-shrink outline package (TSSOP) is contained within the layers. The tag stack-up is described in the following table.
TABLE 1Tag StructureLayerDescription(Driver Side)—LabelWhite Polyethylene Terephthalate (PET),self-adhesive, applied by TransCoreOver-laminateWhite vinyl, self-adhesiveSolderEutectic Sn/Pb, No CleanImmersion SilverApplied to Copper surfaces on chip side oftag to prevent corrosion and enhancesolderabilityLaminateCopperAdhesivePETAdhesiveCopperOrganic SurfaceApplied to Copper surfaces on antenna side ofProtectanttag to prevent corrosionFlood Coat Ink2 coats, UV-cure, white in color, and either1 coat, UV-cure, white in color, or1 coat, UV-cure, customer-specified colorOptional Graphic InkApplied by Pad PrintingPSARemove native release liner
FIG. 1 shows how it looks when an RFID tag 10 is installed inside the windshield. FIG. 1 shows the tag 10 having a label 15 and a chamfered corner 16.
The challenge in producing such high volume product is how to ensure that RFID tags sent to customers meet the performance requirements at the operating conditions.